Local Temperature Measurements Research Articles

Experimental study on the radiative heat transfer in a multi-hole porous radiant burner with internal combustion regime

• The effect of internal zone’s height on the radiant efficiency of internal regime. • An increment of 13.1% in radiant efficiency compared to a multi-layer PRB. • A new radiative heat transfer based non-dimensional number is defined. • The radiative non-dimensional number is only a function of geometry, not power. • The maximum radiant efficiency is occurred at the equivalence ratio of 0.9. An experimental study was performed on the radiative heat transfer in a porous radiant burner (PRB) with an internal combustion regime (ICR). A multi-hole plate and a high pore density SiC porous foam were used to form the jet-shaped flames and the ICR, respectively. For local temperature measurement, a movable Cartesian mechanism is used for the thermocouple. The effects of three independent parameters of input power, P , equivalence ratio, ϕ , and the distance between the multi-hole plate and porous medium (PM), d , on radiative surface temperature and radiant efficiency are investigated. The results show that the radiant efficiency increases 13.1% compared to a multi-layer PRB in the literature at the same firing rate. In addition, the maximum radiant efficiency for all operating conditions occurred at ϕ = 0.9 . Moreover, the radiative surface temperature decreases, a decrease of 2.25%, by increasing d from 85 mm to 145 mm at P , ϕ = 8.25 k W , 0.9 . However, the radiative heat transfer of the PM, as well as the radiant efficiency, does not decrease sharply due to the view factor increment by increasing d . Furthermore, it was concluded that a new non-dimensional number, related to the radiative heat transfer, can be defined by dividing the radiative heat transfer to the burner’s outside to the radiative heat transfer to the burner’s side walls. This heat transfer based non-dimensional number is only a function of d , and it behaves like an ascending function that is independent of input power.

Polymer Micro and Nanoparticles Containing B(III) Compounds as Emissive Soft Materials for Cargo Encapsulation and Temperature-Dependent Applications.

Polymer nanoparticles doped with fluorescent molecules are widely applied for biological assays, local temperature measurements, and other bioimaging applications, overcoming several critical drawbacks, such as dye toxicity, increased water solubility, and allowing imaging of dyes/drug delivery in water. In this work, some polymethylmethacrylate (PMMA), polyvinylpyrrolidone (PVP) and poly(styrene-butadiene-styrene) (SBS) based micro and nanoparticles with an average size of about 200 nm and encapsulating B(III) compounds have been prepared via the reprecipitation method by using tetrahydrofuran as the oil phase and water. The compounds are highly hydrophobic, but their encapsulation into a polymer matrix allows obtaining stable colloidal dispersions in water (3.39 µM) that maintain the photophysical behavior of these dyes. Although thermally activated non-radiative processes occur by increasing temperature from 25 to 80 °C, the colloidal suspension of the B(III) particles continues to emit greenish light (λ = 509 nm) at high temperatures. When samples are cooling back to room temperature, the emission is restored, being reversible. A probe of concept drug delivery study was conducted using coumarin 6 as a prototype of a hydrophobic drug.

Turbulence model assessment and heat transfer phenomena inside a rectangular channel under forced and mixed convection

A very high-temperature gas-cooled reactor (VHTR) is an attractive option for hydrogen production due to its high operating temperature. The reactor cavity cooling system (RCCS), a passive safety system of the VHTR, surrounds the reactor vessel with rectangular riser channels and removes decay heat from it. Under emergency operation conditions such as a decrease in the flow rate of the RCCS, the flow condition inside the RCCS riser can become a mixed convection condition accompanying heat transfer deterioration. To design and operate the VHTR with reliable safety, accurate predictions for various convective heat transfer conditions in RCCS riser channels are required. In this study, by comparing the results of an air flow visualization experiment, the predictability of the turbulence models was assessed for the convective heat transfer and complex flow characteristics near the corner region of the rectangular duct confirmed from the experimental study. In this paper, the heat removal rate through the test section of the visualization experiment was quantified under various convective heat transfer conditions, and local temperature measurement data from the experiment were presented to describe the heat transfer deterioration phenomena inside a rectangular riser in turbulent mixed convection. Linear and nonlinear eddy viscosity models were evaluated by comparing the heat transfer coefficient, local temperature, local flow structure including secondary flow, and turbulence quantities obtained from the experiment. Furthermore, improvements to turbulence models for enhancing the prediction of mixed convection heat transfer in rectangular riser ducts were proposed.

Development of a multi-functional multi-probe atomic force microscope system with optical beam deflection method.

We developed a multi-probe atomic force microscope (MP-AFM) system with up to four probes and realized various functions such as topography mapping, probing electrical property, and local temperature measurement. Each probe mounted on the corresponding probe scanner was controlled independently, and the system employed the optical beam deflection method to measure the deflection of each cantilever. A high-performance MP-AFM system with a compact optical designand rigid actuators was finally established. We demonstrated AFM high-resolution imaging in air and performed four-probe imaging in parallel and multi-functional characterization with the MP-AFM system.

Effect of Radio Frequency Signals on Resistive Measurements of Temperature

In many situations, the measurement of temperature is done with resistive sensors. This is the case with standard platinum resistance thermometers (SPRTs), industrial level PRTs, resistance temperature detectors (RTDs) and thermistors. There are many possible sources of uncertainty in these measurements. One potential source of error that may be difficult to quantify is the error due to radio frequency (RF) signals. This paper presents data from experimentation done with radio signals close to a temperature measurement location. While the data presented in this paper were not taken in a controlled RF measurement laboratory, they are done in a practical situation. The factors such a type of antenna used, walls between the antenna and measuring sensor, distance between the measuring sensor, and the RF source and length of the temperature sensor leads are disclosed. Different factors are considered such as frequency of the RF signal, power of the RF signal, resistance of the temperature probe and length of the temperature probe leads. Amateur radio equipment is used for the RF signal generation in the high frequency (HF), very high frequency (VHF) and ultra high frequency (UHF) bands. The author uses his knowledge of both amateur radio equipment and temperature metrology to present and analyze the data.

Sequential estimation of the time-dependent heat transfer coefficient using the method of fundamental solutions and particle filters

In many thermal engineering problems involving high temperatures/high pressures, the boundary conditions are not fully known since there are technical difficulties in obtaining such data in hostile conditions. To perform the task of estimating the desired parameters, inverse problem formulations are required, which entail to performing some extra measurements of certain accessible and relevant quantities. In this paper, justified also by uniqueness of solution conditions, this extra information is represented by either local or non-local boundary temperature measurements. Also, the development of numerical methods for the study of coefficient identification thermal problems is an important topic of research. In addition, in order to decrease the computational burden, meshless methods are becoming popular. In this article, we combine, for the first time, the method of fundamental solutions (MFS) with a particle filter sequential importance resampling (SIR) algorithm for estimating the time-dependent heat transfer coefficient in inverse heat conduction problems. Two different types of measurements are used. Numerical results indicate that the combination of MFS and SIR shows high performance on several test cases, which include both linear and nonlinear Robin boundary conditions, in comparison with other available methods.

Hybrid Nanocomposites Formed by Lanthanide Nanoparticles in Zr-MOF for Local Temperature Measurements during Catalytic Reactions

Zr-metal organic frameworks (MOFs) are waterstable materials with high surface properties and chemical stabilities and are often employed for catalysis. They can also become hosts for various upconverting nanoparticles via selfassembly, which opens up possibilities to use such nanocomposite materials for combined catalysis-thermometry applications. In our work, we show that the NaGdF4:Er, Yb@UiO-66-NH2, NaGdF4:Tm,Yb@UiO-66-NH2, and NaYF4:Er,Yb@NaYF4@UiO-66-NH2 nanocomposite materials display excellent temperaturedependent luminescence properties. Additionally, these nanocomposite materials can perform as a stable and reusable catalyst for the esterification of lauric acid (biomass-derived free fatty acid) with methanol to obtain methyl laurate. The NaGdF4/NaYF4 nanoparticles incorporated in the MOF do not significantly decrease their catalytic performance. At the same time, photoluminescence measurements can be performed in a working catalytic environment and the temperature can be read out from the ratio of the H-2(11/2) and S-4(3/2) transition peaks of Er3+ or F-3(3) and H-3(4) transition peaks of Tm3+ from the nanocomposites. The correlation between temperature, luminescent intensities, and catalytic reactivity was studied and showed that all the three factors depend on each other, but do not interfere. To the best of our knowledge, the combination of catalysis and luminescence thermometry in a MOF hybrid material has not been reported to date. However, it opens a wide range of possibilities, keeping in mind the large and versatile number of MOFs as well as different thermometry systems that can be incorporated into inorganic nanoparticles.

Real-time temperature measurement in stochastic rotation dynamics.

Many physical and chemical processes involve energy change with rates that depend sensitively on local temperature. Important examples include heterogeneously catalyzed reactions and activated desorption. Because of the multiscale nature of such systems, it is desirable to connect the macroscopic world of continuous hydrodynamic and temperature fields to mesoscopic particle-based simulations with discrete particle events. In this work we show how to achieve real-time measurement of the local temperature in stochastic rotation dynamics (SRD), a mesoscale method particularly well suited for problems involving hydrodynamic flows with thermal fluctuations. We employ ensemble averaging to achieve local temperature measurement in dynamically changing environments. After validation by heat diffusion between two isothermal plates, heating of walls by a hot strip, and by temperature programed desorption, we apply the method to a case of a model flow reactor with temperature-sensitive heterogeneously catalyzed reactions on solid spherical catalysts. In this model, adsorption, chemical reactions, and desorption are explicitly tracked on the catalyst surface. This work opens the door for future projects where SRD is used to couple hydrodynamic flows and thermal fluctuations to solids with complex temperature-dependent surface mechanisms.

MEASUREMENT OF THE LOCAL ELECTRON TEMPERATURE IN SELF-COMPRESSED PLASMA STREAM

The local electron temperature measurements with the double electric probe in the compression zone are presented. Electric probes make it possible to measure the electron temperature with a reasonably good spatial resolution. Double electric probe application for electron temperature measurements in the dense self-compressed plasma stream is discussed. We have shown experimentally that the electric probe operates in a diffusion regime.

Effect of the Heat Transfer Coefficient Reference Temperatures on Validating Numerical Models of Supercritical CO2

Abstract Validating turbulence models for cooling supercritical carbon dioxide (sCO2) in a horizontal pipe is challenging due to the lack of experimental data with spatially resolved local temperature measurements. Although many variables may be present to cause discrepancies between numerical and experimental data, this study focuses on how the choice of reference temperatures (both wall reference temperature and fluid bulk reference temperature) when calculating the heat transfer coefficient influences turbulence-model validation results. While it may seem straightforward to simply use the same parameters as the experimental setup, this has not been observed in practice. In this work, numerical simulations are performed for cooling sCO2 in a horizontal pipe for p = 8 MPa, d = 6 mm, G = 200, and 400 kg/(m2s), and qw = 12, 24, and 33 kW/m2. Local and average heat transfer coefficients with different reference temperatures, found to be frequently used in the literature, are presented and compared with commonly used experimental data. It was found that the choice of reference temperatures has a significant influence on the results of the numerical validation. Historically, the higher heat flux cases have been more difficult to validate, theorized due to using reference temperatures differing from the experiment; however, good agreement was found here using the reference temperatures that most closely matched the experiment. This not only highlights the need for careful selection of reference temperatures in simulations, but also the importance of clearly defining the reference temperature employed when reporting experimental results.

Reduced order modelling for spatial-temporal temperature and property estimation in a multi-stage hot sheet metal forming process

A concise approach is proposed to determine a reduced order control design oriented dynamical model of a multi-stage hot sheet metal forming process starting from a high-dimensional coupled thermo-mechanical model. The obtained reduced order nonlinear parametric model serves as basis for the design of an Extended Kalman filter to estimate the spatial-temporal temperature distribution in the sheet metal blank during the forming process based on sparse local temperature measurements. To address modeling and approximation errors and to capture physical effects neglected during the approximation such as phase transformation from austenite to martensite a disturbance model is integrated into the Kalman filter to achieve joint state and disturbance estimation. The extension to spatial-temporal property estimation is introduced. The approach is evaluated for a hole-flanging process using a thermo-mechanical simulation model evaluated using LS-DYNA. Here, the number of states is reduced from approximately 17 000 to 30 while preserving the relevant dynamics and the computational time is 1000 times shorter. The performance of the combined temperature and disturbance estimation is validated in different simulation scenarios with three spatially fixed temperature measurements.

Electric pulse heating device for the analysis of solid/solid phase transformations.

Ohmic pulse heating is applied to investigate diffusion and interface controlled solid-state phase transformations. The developed device uses extensive solid-state electronics providing a high current, low voltage approach that overcomes the limitations of existing setups, most notably the use of sample geometries that allow for the reliable measurement of local temperatures and their assignment to microstructures. Power for heating is supplied by a capacitor array with adjustable voltage, and the process is controlled by microcontrollers and a solid-state relay, which allows for controlled pulses that are adjustable in microseconds. Electric currents of up to 22 kA at 90V can be realized by the setup. Electric data are monitored and collected during the experiments, and temperature data are captured using a high-resolution infrared camera at high frame rates (1200fps). The capabilities of the setup are demonstrated by rapid heating (106 K/s) and subsequent cooling of a brass sample. Two distinct areas of the sample are analyzed in detail, showing similar heating, but different cooling curves with rates of 104 and 102 K/s. Local microstructure analysis shows that different phase transformation mechanisms were dominant, and thus, the setup fulfills its purpose.

COMPARISON OF METHODS FOR CONTROLLED THERMAL DEFORMATIONS IN MACHINE TOOLS

Progress in improving the accuracy of metal-cutting machines is inextricably linked and driven by deeper knowledge gained through the study of thermal processes and effects occurring in machines, which can be used to manage them. This led to the dominance of temperature errors in the balance of machine accuracy, the share of which changed from 20-30% to 70% during the period from 1950 to 2020, which is determined by the absolute value of the achievable machine accuracy. Types and forms of compensation methods were formed (1990-2020), which were based on the use of linear and nonlinear regression or correlation methods. Performing experiments can establish the functional relationship between the measured temperature in the machine nodes and the amount of displacement. With good repeatability and stable reproducibility of the result, an equation expresses this functional relationship. Applying this equation to a program, a control device compensates the thermal deformations. However, in all cases, it is necessary to determine the number and location of temperature measurements on the machine, determining the compensation accuracy. The proposed sensorless model is based on a thermal behavior model and does not require temperature measurements. A method is presented and justified for estimating the number of temperature measurement locations based on thermophysical analysis by applying the finite element method in comparison with the analytical method in order to achieve the required compensation accuracy. For several machine tool types, a comparison is given regarding the control method of the TCP spindle displacement without sensors and with temperature sensors. The limits of their rational use are presented.

Fast and Localized Temperature Measurements During Simulated Earthquakes in Carbonate Rocks.

The understanding of earthquake physics is hindered by the poor knowledge of fault strength and temperature evolution during seismic slip. Experiments reproducing seismic velocity (∼1 m/s) allow us to measure both the evolution of fault strength and the associated temperature increase due to frictional heating. However, temperature measurements were performed with techniques having insufficient spatial and temporal resolution. Here we conduct high velocity friction experiments on Carrara marble rock samples sheared at 20 MPa normal stress, velocity of 0.3 and 6 m/s, and 20 m of total displacement. We measured the temperature evolution of the fault surface at the acquisition rate of 1 kHz and over a spatial resolution of ∼40 µm with an optical fiber conveying the infrared radiation to a two‐color pyrometer. Temperatures up to 1,250°C and low coseismic fault shear strength are compatible with the activation of grain size dependent viscous creep.

A theoretical framework for classifying occupant-centric data streams on indoor climate using a physiological and cognitive process hierarchy

New and pervasive information and communication technologies have made it possible to capture a large range of continuous data from, or close to, each individual building occupant. These occupant-centric data streams may include subjective votes, evaluations, complaints, control actions, physiological measurements such as heart rate or pupil size, physical measurements of skin temperature or local draft and air temperature measurements, and much more. Currently, considerable resources are put into studies that focus on the development and potential uses of such systems, while the origin and nature of the collected information which is embedded in the data is poorly investigated. In this paper, we propose a taxonomy for the classification of occupant-centric data streams, developed through the application of established theories and categories in environmental and market psychology. The proposed framework organises five data source categories and links them to four levels of physiological and cognitive processes, making an explicit connection between data and embedded information attributes. The framework, originally developed to classify continuous occupant centric data in the domain of indoor climate, can also bring insights that might help explain known gaps and challenges in different models and theories that aim at predicting individual satisfaction with indoor climate conditions.

Correlation of local strain and temperature measurements in confocal Raman microscopy

AbstractIn microsystem technologies, it is very common to employ Raman spectroscopy to monitor the strain generated during the fabrication of microelectromechanical systems and integrated circuits devices, an example being through‐silicon vias. Typically, for strain analysis, the laser intensity is chosen to be sufficiently low to avoid the laser heating affecting the position of the Raman lines under consideration, because theoretically, the measured strain can have two origins: for one as a consequence of mechanical stress through Hooke's law, and for the other, as a consequence of temperature. The latter has often been overlooked throughout literature. Here, we revisit a couple of cases, for which tensile strain is detected, by comparing them to Raman analysis on samples of empty through‐silicon vias, that were expected to be strain free. By simultaneously monitoring strain and the local temperature through the ratio of anti‐Stokes to Stokes lines, it is found that at least part of the strain usually attributed to mechanical stress can be quantitatively attributed to laser‐induced thermal expansion, even at relatively low laser intensities. We support our findings using a finite element model and present key implications on the interpretation of strain measurements in copper‐filled through‐silicon vias.

Phase relation between rotating phase locked (2, 1) and (3, 1) tearing modes in ASDEX Upgrade

Tearing modes are a major concern for large tokamak devices. Therefore their detection and characterization is of importance for timely countermeasures to avoid significant impact on the discharge or at least prevent possible machine damage. In case of phase-locked tearing modes, the poloidal variation of induced magnetic field fluctuation depends on the amplitudes of and the phase difference between the individual modes. This affects mode detection and identification when not considered appropriately. The phase between phase-locked (2, 1) and (3, 1) tearing modes in ASDEX Upgrade has been determined from local electron temperature and magnetic measurements independently. It is shown that the modes can be in phase at any poloidal position starting from the low field side plasma midplane over the plasma top to the high field side midplane. This observation invalidates the widespread assumption that phase-locked tearing modes are in phase near the low field side midplane. Dependence of the in-phase position on both, the plasma pressure and the plasma rotation velocity, is observed.

Distributed fiber optic measurements of strain and temperature in long-span composite floor beams with simple shear connections subject to compartment fires

This study explores an instrumentation strategy using distributed fiber optic sensors to measure strain and temperature through the concrete volume in large-scale structures. Single-mode optical fibers were deployed in three 12.8 m long steel and concrete composite floor specimens tested under mechanical or combined mechanical and fire loading. The concrete slab in each specimen was instrumented with five strain and temperature fiber optic sensors along the centerline of the slab to determine the variation of the measurands through the depth of the concrete. Two additional fiber optic temperature sensors were arranged in a zigzag pattern at mid-depth in the concrete to map the horizontal spatial temperature distribution across each slab. Pulse pre-pump Brillouin optical time domain analysis (PPP-BOTDA) was used to determine strains and temperatures at thousands of locations at time intervals of a few minutes. Comparisons with co-located strain gauges and theoretical calculations indicate good agreement in overall spatial distribution along the length of the beam tested at ambient temperature, while the fiber optic sensors additionally capture strain fluctuations associated with local geometric variations in the specimen. Strain measurements with the distributed fiber optic sensors at elevated temperatures were unsuccessful. Comparisons with co-located thermocouples show that while the increased spatial resolution provides new insights about temperature phenomena, challenges for local temperature measurements were encountered during this first attempt at application to large-scale specimens.

Applying the handprint approach to assess the air pollutant reduction potential of paraffinic renewable diesel fuel in the car fleet of the city of Helsinki

Abstract Ambient air pollution is a global environmental challenge, especially in densely populated regions. In urban areas, road traffic is an important source of fine particulate matter (PM2.5) and nitrogen oxide (NOx) emissions, primarily due to exhaust gases. The adoption of paraffinic renewable diesel fuels for urban transportation has been suggested as a more sustainable and less air polluting alternative to conventional fossil fuels. The aim of this study is, therefore, to examine whether the transition from the conventional fossil fuel diesel to paraffinic renewable diesel (hydrotreated vegetable oil [HVO] according to the EN 15940 standard) can reduce PM2.5 and NOx emissions in an urban environment. The life cycle assessment-based handprint approach is utilized to calculate and demonstrate the emissions reduction. The reduction potential is quantified for Euro 4, 5 and 6 passenger diesel cars using actual car fleet, mileage, local temperature, and laboratory emissions measurements for 2018 in Helsinki, Finland. Our study shows that the use of HVO can reduce PM2.5 and NOx emissions in urban areas. According to our results, PM2.5 emissions could be reduced by 49% for the defined location and car fleet by replacing conventional fossil-fuel diesel with HVO. In the case of NOx emissions, the local reduction potential is 7%. Overall life cycle emissions reduction potentials of NOx and PM2.5 emissions are 11% and 44%, respectively, if conventional diesel is replaced by HVO. Thus, the manufacturer of HVO can communicate the air quality handprint, and in particular, the NOx and PM2.5 handprints, that their product can achieve.

Experimental measurement of local high temperature at the surface of gold nanorods using doped ZnGa2O4 as a nanothermometer.

Heat measurement induced by photoexcitation of a plasmonic metal nanoparticle assembly under environmental conditions is of primary importance for the further development of applications in the fields of (photo)catalysis, nanoelectronics and nanomedicine. Nevertheless, the fine control of the rise in temperature remains difficult and limits the use of this technology due to the lack of local temperature measurement tools working under environmental conditions. Luminescence nanothermometers are an alternative solution to the limitations of conventional contact thermometers since they are able to give an absolute temperature value with high spatial resolution using common optical equipment. As a proof of concept of this nanothermometry approach, a high local temperature exceeding one hundred degrees is measured on the thermalized photoexcited aggregate of gold nanorods using ZnGa2O4:Cr3+,Bi3+ nanothermometers that have a strong temperature dependence on the luminescence lifetime of chromium(iii) and high sensitivity over an extensive range of temperatures. A study on the influence of the average distance between nanosensors and nanoheaters on the measured temperature is carried out by coating the nanosensors with a silica layer of tunable thickness, highlighting the temperature gradient at the vicinity of the nanoheater as the theory predicts. The variation of the optical nanosensor response is relevant and promising, and it could be further envisioned as a potential candidate for local temperature measurement at the nanoscale since no plasmonic effect on Cr3+ lifetime is observed. The results reported here open up an even wider field of application for high temperature nanothermometry on real samples such as aggregate particles for many applications including catalysis and nanoelectronics. Thermometry using luminescent nanoprobes, which is complementary to thermal microscopy techniques, will allow in situ and in operando temperature monitoring at very small scales.